This invention relates to an air circuit breaker and more particularly, a rebound prevention device to effect a controlled opening during OFF-operation of the air circuit breaker.
This type of circuit breaker uses a link mechanism and a trip mechanism for opening and closing both fixed and movable contact pieces. The operation of the link mechanism is done by utilizing resilient force of a spring to be actuated by operation of the trip mechanism. Since the opening and separating action of the contact pieces need to be done instantaneously, a spring having a strong resilient force is usually employed. With such spring of a strong resilient force, however, there takes place a bouncing or spring-back phenomenon, and, in an extreme case, re-ignition occurs inevitably. In order, therefore, to prevent this bouncing phenomenon from taking place in the contact opening and closing mechanism, there have so far been proposed various expedients with no fruitful result of any bounce preventive mechanism, which is most reliable in its operation, having been realized.